Project Summary Isotretinoin is a vitamin A analogue used to treat severe inflammatory, nodular acne in over 13 million people, including children, since its availability in 1982. Isotretinoin causes atrophic changes in the sebaceous gland acini with a marked decrease in sebum production by altering gene expression and promoting inflammatory mediator expression in meibomian gland (MG) epithelial cells. Its teratogenic effects have also led to the implementation of United States Food and Drug Administration's Risk Evaluation Mitigation Strategy program in 2006, called iPLEGDE, which was designed to prevent possible isotretinoin pregnancy exposures in females of child-bearing potential by requiring these patients to incorporate two forms of birth control into their therapy. Hormonal birth control (HBC) containing a combination of estrogen and progesterone is a viable option, since it meets the iPledge requirement and is an effective treatment for some forms of acne. HBC exerts its effect by decreasing androgen production and serum free testosterone levels, which can have profound effects on the sex hormone-regulated MGs. Androgens have been shown to increase lipid metabolism and transport, downregulate genes associated with keratinization of epithelial cells, and suppress pro-inflammatory responses throughout the body, including the eye. The proposed research aims to elucidate the short- and long-term effects of isotretinoin therapy on the ocular surface in vivo, including the structure and function of MGs. The first aim is to estimate the relative risk and risk factors of having MG atrophy due to previous isotretinoin exposure. This will be achieved through a single-timepoint cohort study by surveying participants about their history of isotretinoin use prior to conducting a complete ocular surface examination. The second aim is to estimate the incidence ratio and attributable risk of MG atrophy due to isotretinoin therapy, incidence rate of MG recovery after treatment, and natural history of MG structure and meibum composition over 18 months. This will be accomplished through a prospective cohort study involving ocular surface examinations and meibum collection at baseline, each month during treatment, and six and 12 months after discontinuing treatment. The study population will consist of three female cohorts (isotretinoin+HBC, HBC only, untreated). A sample of each patient's meibum will be collected at each visit for lipidomic analysis. Given the volume of patients who are treated with isotretinoin annually, the results of this study can influence future therapeutic decisions and dermatological and ophthalmic management plans for isotretinoin patients.